Confession time: I have made supreme messes with categories in the past. One blog had, at its worst, 83 categories - of which more than a dozen only had one post in them. Another went to the opposite extreme, and had one single category called "Stuff". Again, hardly helpful. Adding the possibility of tags as well just made this worse: is "stuff" a category or a tag?

Any blogger is free to use tags and/or categories in any way they choose: if you want to ignore both and dump all your posts into one big pot, it's your blog after all. But tags and categories can be useful in helping your readers find the content they want, albeit in very different ways, so it's worth thinking more carefully about the way you use them.

Everything's categorised, even if it's Uncategorised

The obvious functional difference in WordPress is that every post you write has to be in a category. On a fresh WP install, there is one category: "Uncategorised". Even if you create a bunch of more meaningful categories and delete Uncategorised, there still has to be a default category into which otherwise uncategorised posts go. It's worth making the title of this default category something usefully catch-all for those posts that don't quite fit the normal topics of your blog: on TameBay we call it "News", and on my personal blog it's "Self-Indulgence".

On the other hand, there is nothing in the WP system forcing you to use tags.

Categories are hierarchicial : tags cross-connect

The other practical WP difference between tags and categories is that the latter are hierarchical: categories can have sub-categories (and sub-sub-categories); tags cannot. Use categories to organise your content: as you can generate navigation menus directly from WP categories (see, for example, the drop-downs from the lighter grey bar across the top of TameBay, which are all subcategories), it makes sense to use them structurally in your site.

Tags cut across such structures. To take another example from TameBay, we might talk about Meg Whitman in the category Events, when she spoke at eBay Live; in Site Changes, when she announced some fee change; or in News, now she's running for Governor of California. As our topic is ecommerce, having a "Meg Whitman" category doesn't really make much sense, but tagging all of the posts in which she appears does, and drives some search engine traffic via that tag's archive page. If, however, we were running a blog about the Californian elections, we'd certainly want "Meg Whitman" as a category.

Lorelle summed all this up most succinctly: "I think of categories as a table of contents and tags as the index page of a book." Or as Carthik Sharma said, "Categories are like the huge signs you see on aisles in supermarkets - 'Food', 'Hygiene', 'Frozen' etc, they guide you to sections where you can find what you are looking for. Tags are like the labels on the products themselves."

Categories should be limited; tags needn't be

Because categories organise, I prefer to use as few as possible. Using a different category whenever I possibly could would feel like writing a book in which each paragraph was a separate chapter. But tags can usefully proliferate into dozens and even hundreds as your blog grows. WordPress itself encourages this behaviour: when you write a new post, categories are selectable boxes, but tags are a free-form text box, to which you can add as many as you like.

Even so, tags need to be controlled to be useful to your readers. A tag that's only used on one post doesn't help anyone find related content, after all. The link to "choose from the most popular tags" when you post can be helpful, as it encourages tag re-use, so keeping related topics closer together. Think of tags as clickable site search and you won't go far wrong with them.

Tag clouds : not just for tags any more

Before now, I'd have also said that only tags can be used to generate a tag cloud. But from WordPress 2.8, due out some time this month, both post categories and links categories will also be available to have tag clouds generated from them. Good news for people who like tag clouds; utterly terrible news for usability.

This question came via the Skribit widget in my sidebar: if there’s a question you’d like answered, please post it!

Tags: categories, Lorelle, Skribit, tags, WordPress

Posted by Sue on April 5, 2009 in WordPress.